Analysis of cache for streaming tape drive

A tape subsystem consists of a controller and a tape drive. Tapes are used for backup, data interchange, and software distribution. The backup operation is addressed. During a backup operation, data is read from disk, processed in CPU, and then sent to tape. The processing speeds of a disk subsystem, CPU, and a tape subsystem are likely to be different. A powerful CPU can read data from a fast disk, process it, and supply the data to the tape subsystem at a faster rate than the tape subsystem can handle. On the other hand, a slow disk drive and a slow CPU may not be able to supply data fast enough to keep a tape drive busy all the time. The backup process may supply data to tape drive in bursts. Each burst may be followed by an idle period. Depending on the nature of the file distribution in the disk, the input stream to the tape subsystem may vary significantly during backup. To compensate for these differences and optimize the utilization of a tape subsystem, a cache or buffer is introduced in the tape controller. Most of the tape drives today are streaming tape drives. A streaming tape drive goes into reposition when there is no data from the controller. Once the drive goes into reposition, the controller can receive data, but it cannot supply data to the tape drive until the drive completes its reposition. A controller can also receive data from the host and send data to the tape drive at the same time. The relationship of cache size, host transfer rate, drive transfer rate, reposition, and ramp up times for optimal performance of the tape subsystem are investigated. Formulas developed will also show the advantages of cache watermarks to increase the streaming time of the tape drive, maximum loss due to insufficient cache, tradeoffs between cache and reposition times and the effectiveness of cache on a streaming tape drive due to idle times or interruptions due in host transfers. Several mathematical formulas are developed to predict the performance of the tape drive. Some examples are given illustrating the usefulness of these formulas. Finally, a summary and some conclusions are provided

HET acid based oligoesters – TGA/FTIR studies

One of the important reactive halogenated dicarboxylic acids used in the synthesis of flame retardant unsaturated polyester resins is 1,4,5,6,7,7-hexachlorobicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid (HET acid). In the present investigation four different oligoesters are synthesized using HET acid as the diacid component and 1,2-ethane diol, 1,2-propane diol, 1,3-propane diol and 1,4-butane diol as the aliphatic diols. Melt condensation technique in vacuum is used for the synthesis of the oligoesters. The number average molecular weights of the oligoesters are determined using end group analysis. The degree of polymerization is estimated to be 3–5. The structural characterization is done using FTIR and NMR (1H and 13C) techniques. In the present investigation, TGA-FTIR studies for the different oligoesters are carried out in nitrogen atmosphere. The materials are heated from ambient to 600 °C at a heating rate of 20 °C/min. The main volatile products identified are CO, HCl, H2O, CO2, hexachlorocyclopentadiene and HET acid/anhydride. The evolution profile of these materials with respect to the structure of the oligoesters is discussed in detail and presented. The importance of β-hydrogens in the diol component and the plausible mechanism for the flame retardant behavior of these oligoesters are presented

Thermal Degradation Studies on PMMA–HET Acid Based Oligoesters Blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented

Climate change impact reliability of large electric power transformers in the Northeast United States

Global climate model simulations, when scaled to the Northeast U.S. region, indicate that New England will by 2100 experience many more days each summer of daily maximum temperatures in excess of 90°F. Given the strong correlation between summer heat waves and electric power demand, the stresses placed on the components of the electric grid by prolonged, elevated power demand is of obvious concern. In this thesis a standard thermal model for large transformers is coupled with a temperature-dependent electric power demand model to predict the frequency of transformer thermal overload events during the months of June, July, and August through the year 2099. The coupled demand/thermal model was driven by a projected daily maximum temperature time series extracted from the original datasets of the 2007 Northeast Climate Impacts Assessment of the Union of Concerned Scientists. The results of the calculations show that transformers loaded at 70% or less of their nameplate rating will not experience any significant increase in the frequency of thermal overload events even if New England\u27s climate becomes substantially warmer. However, transformers loaded at 80% or more of their nameplate rating will experience an increasing frequency of thermal overload events in each of the summer months as time progresses to 2100. Ideas are presented for mitigating the increased likelihood of transformer thermal overload events

Effects of Age and Retinal Degeneration on the Expression of Subtilisin-like Proprotein Convertases in the Visual Cortex of Mice

Postnatal development of the visual cortex is a complex process that involves a number of molecules like growth factors, neuropeptides and cholesterol. Neurotrophins, like NGF, BDNF, NT-3, and NT-4, which are synthesized as precursors, also play a very important role in visual cortex development. Subtilisin-like proprotein convertases (SPCs) play a vital role in the limited endoproteolysis of precursors of secretory proteins that participate in development, homeostasis and in numerous pathologies. SPCs also process pro-neurotrophins into mature forms which facilitates neuron survival and differentiation through binding of the neurotrophins Trk receptors. In contrast, unprocessed forms of neurotrophins bind to the p75NTR death receptor and cause apoptosis. We studied the expression pattern of SPCs during postnatal development of the visual cortex in wild type mice (wt) and retinal degeneration mice (rd) using quantitative real-time PCR. The widely expressed SPCs showed a similar pattern of expression during development with high levels of mRNA early in postnatal development. The expression pattern of SPCs was total different in rd mice. Lower levels of expression of both widely expressed adn tissue-specific SPCs were seen at week 1. PCSK9 also showed a significant difference in expression. PCSK9 might play an important role in synaptic formation by regulating the uptake of cholesterol. This difference in expression pattern of SPCs during development and retinal degeneration support the hypothesis that SPCs play a critical role duirng brain development and nuerodegenerative diseases. Understanding the potential role of SPCs in neurdegenerative diseases may lead to new targets for treating such diseases.Master'sCollege of Arts and Sciences: BiologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/117684/1/Chinnaswamy.pd

Air Pollution in Bangalore, India: A Six-Year Trend and Health Implication Analysis

Air pollution is increasingly becoming a global concern and is believed to be amongst the leading causes of death in the world today. Developing countries, with rapidly growing economies, are struggling between the focus on economic development and curbing air pollution emissions. Bangalore is one of India’s fastest growing metropolises and, although benefiting economically due to its rapid development, has a rapidly deteriorating environment. This paper provides a critical analysis of the air pollution trend in the city over the period 2005-2011 at 6 specific locations where measurements have been consistently recorded. It also discusses the potential health implications pertaining to exceeding levels of pollutants where these are applicable

Spatial Interpolation of Air Pollutants in Bangalore: 2010-2013

Air pollutants and their ill effects on the environment and health of populations are well known. However for informed decisions on the protection of the health of populations from elevated levels of air pollution, an understanding of spatial-temporal variance of air pollutant patterns is necessary. Bangalore and other similar developing cities do not have an adequate number of fixed monitoring stations that could provide a complete coverage of the air pollution levels for the entire city. This can be overcome by using geospatial interpolation techniques that provide a complete coverage of the levels of pollutants. The aim of this study is to locate sample points, characterise distribution patterns, map air pollutant distributions using interpolation techniques, highlight areas exceeding standard levels and in doing so determine spatial and temporal patterns of the levels of air pollutants. An air pollution map indicating levels of the variability of the pollutants will aid in the analysis of effects on health in populations due to elevated levels of pollutants

Editorial: Why should we read Dalit literature?

http://journals.sagepub.com/toc/jcla/0/0Numéro spécial papier publié en 2019International audienc

The Impact of Surface Roughness on Transonic Compressor Performance

The increasing necessity for highly efficient engines and flow emission standards has steered the need for research into more efficient design and optimization of gas turbines. Surface roughness in the blades of compressors and turbines is one of the factors causing performance deterioration in gas turbines. This study involves the investigation of surface roughness effects on the performance of a research compressor stage through numerical simulations in a commercial CFD code, ANSYS CFX. An initial numerical study on a NACA airfoil was conducted with roughness and validated with the experimental data. It is followed by the implementation of uniform sand grain roughness over the rotor and stator blades of the compressor stage using the surface roughness model available in ANSYS CFX. Two different cases, one with roughness on the rotor and one with roughness on the stator and rotor combination were done. The results from the study shows the reduction in the main performance parameters such as pressure ratio, efficiency and mass flow in the compressor stage. The flow calculations shows an increase in blockage of the flow in the stage with an increase in surface roughness on the blades. Surface streamlines shows the influence of surface roughness on the separation over the suction side of the stator and the regions near the hub in the rotor